The present invention deals with novel curable fluorosilicone masses that are especially useful as elastomers and coatings.
Silicone coatings in general are quite well known. Pertinent to the present invention among silicone coatings are the curable silicone compositions described in U.S. Pat. No. 4,322,518, issued Mar. 30, 1982 to J. Blizzard and assigned to the assignee of the present invention. In said U.S. Patent compositions are disclosed which comprise: (1) certain liquid copolymeric organopolysiloxanes comprising SiO.sub.4/2 units, silicon-bonded hydroxy radicals, and/or silicon bonded hydrogen radicals, and (2) a polydiorganosiloxane in which the organic radical substituents are monovalent hydrocarbon radicals. Each polydiorganosiloxane molecule cotains at least two vinyl radicals or silicon-bonded hydroxy radicals, on average.
Silicone elastomers and coatings, such as those described in U.S. Pat. No. 4,322,518 have been successful in furnishing beneficial properties. For example, silicone elastomers and coatings have good release of normally adherent materials, low temperature flexibiliity, resistance to degradation at elevated temperatures, and a variety of other beneficial properties. Additionally, silicone elastomers and coatings are easy to fabricate, such as by coating onto a substrate, by extrusion, or by many of the various molding techniques.
Nonetheless, there are certain use environments for elastomers and coatings that require greater resistance to hydrocarbon liquids than is furnished by silicone elastomers and coatings comprising mainly hydrocarbon radical substituents. Examples of some of the more important hydrocarbon liquids include fuels, such as gasoline, kerosene, diesel fuel, light oil and the like; solvents such as naptha, mineral spirits, hexane, pentane, iso-octane, toluene, xylene and the like; edible oils such as corn oil, shortening, peanut oil, olive oil and the like; and other important hydrocarbon liquids.
By resistance to hydrocarbon liquids it is meant herein: maintaining useful mechanical properties and dimensional stability upon prolonged exposure to hydrocarbon liquids. Thus an elastomer that is resistant to hydrocarbon liquids will not substantially swell and will not substantially diminish in, e.g. tensile strength, upon prolonged exposure, such as 30 minutes or more, to hydrocarbon liquids. A hydrocarbon resistant coating so exposed will not dissolve, change substantially in appearance, or swell.
In order to increase the hydrocarbon liquid resistance of silicone elastomers and coatings, various alterations of basic monovalent hydrocarbon-substituted silicone elastomers and coatings have been attempted. One of the more successful of such alterations has been the synthesis and commercial development of silicones substituted with fluorinated hydrocarbons; such silicones are referred to herein as fluorosilicones.
Exemplary of fluorosilicone compositions curable to elastomers is the composition disclosed in U.S. Pat. No. 3,179,619, issued Apr. 20, 1965. Said composition comprises a polydiorganosiloxane polymer containing a high proportion of fluorinated radicals, filler, organic peroxide, and other components. Upon cure, said composition yields elastomers of good mechanical strength. Unfortunately, because of the extremely high viscosity of said composition, application as a thin film, such as 0.025 mm or less in thickness, is difficult, if not impossible.
U.S. Pat. No. 4,041,010 issued Aug. 9, 1977, discloses a two part, room temperature curing fluorosilicone comprising: a vinyl group terminated fluorosilicone polymer; a vinyl-containing polymer or resin; a hydrogen-containing fluorosilicone; and a platinum catalyst.
U.S. Pat. No. 3,050,411, issued Aug. 21, 1962, discloses release coatings consisting essentially of methylhydrogenpolysiloxane, plus a polydiorganosiloane containing fluoroalkyl groups. While excellent release properties and suitable resistance to hydrocarbon solvents are furnished by the coatings of U.S. Pat. No. 3,050,411, said coatings are lacking in the strength furnished by filled, high viscosity fluorosilicone elastomers.
Thus it would be desirable to provide a fluorosilicone composition that is resistant to hydrocarbon liquids, has good strength, and can be conveniently applied to a substrate as a thin film.